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Bestial boredom: a biological perspective on animal boredom and suggestions for its scientific investigation

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Boredom is likely to have adaptive value in motivating exploration and learning, and many animals may possess the basic neurological mechanisms to support it. Chronic inescapable boredom can be extremely aversive, and understimulation can harm neural, cognitive and behavioural flexibility. Wild and domesticated animals are at particular risk in captivity, which is often spatially and temporally monotonous. Yet biological research into boredom has barely begun, despite having important implications for animal welfare, the evolution of motivation and cognition, and for human dysfunction at individual and societal levels. Here I aim to facilitate hypotheses about how monotony affects behaviour and physiology, so that boredom can be objectively studied by ethologists and other scientists. I cover valence (pleasantness) and arousal (wakefulness) qualities of boredom, because both can be measured, and I suggest boredom includes suboptimal arousal and aversion to monotony. Because the suboptimal arousal during boredom is aversive, individuals will resist low arousal. Thus, behavioural indicators of boredom will, seemingly paradoxically, include signs of increasing drowsiness, alongside bouts of restlessness, avoidance and sensation-seeking behaviour. Valence and arousal are not, however, sufficient to fully describe boredom. For example, human boredom is further characterized by a perception that time ‘drags’, and this effect of monotony on time perception can too be behaviourally assayed in animals. Sleep disruption and some abnormal behaviour may also be caused by boredom. Ethological research into this emotional phenomenon will deepen understanding of its causes, development, function and evolution, and will enable evidence-based interventions to mitigate human and animal boredom.
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Essay
Bestial boredom: a biological perspective on animal boredom
and suggestions for its scientic investigation
Charlotte C. Burn
*
The Royal Veterinary College, North Mymms, Hertfordshire, U.K.
article info
Article history:
Received 26 January 2017
Initial acceptance 17 March 2017
Final acceptance 16 May 2017
MS. number: 17-00094R
Keywords:
animal behaviour
animal cognition
animal welfare
boredom
environmental enrichment
motivation
novelty
psychobiology
time perception
Boredom is likely to have adaptive value in motivating exploration and learning, and many animals may
possess the basic neurological mechanisms to support it. Chronic inescapable boredom can be extremely
aversive, and understimulation can harm neural, cognitive and behavioural exibility. Wild and
domesticated animals are at particular risk in captivity, which is often spatially and temporally
monotonous. Yet biological research into boredom has barely begun, despite having important impli-
cations for animal welfare, the evolution of motivation and cognition, and for human dysfunction at
individual and societal levels. Here I aim to facilitate hypotheses about how monotony affects behaviour
and physiology, so that boredom can be objectively studied by ethologists and other scientists. I cover
valence (pleasantness) and arousal (wakefulness) qualities of boredom, because both can be measured,
and I suggest boredom includes suboptimal arousal and aversion to monotony. Because the suboptimal
arousal during boredom is aversive, individuals will resist low arousal. Thus, behavioural indicators of
boredom will, seemingly paradoxically, include signs of increasing drowsiness, alongside bouts of rest-
lessness, avoidance and sensation-seeking behaviour. Valence and arousal are not, however, sufcient to
fully describe boredom. For example, human boredom is further characterized by a perception that time
drags, and this effect of monotony on time perception can too be behaviourally assayed in animals. Sleep
disruption and some abnormal behaviour may also be caused by boredom. Ethological research into this
emotional phenomenon will deepen understanding of its causes, development, function and evolution,
and will enable evidence-based interventions to mitigate human and animal boredom.
©2017 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
Chronic inescapable boredom is neither trivial nor benign. In
Charles Dickens's (1853) novel Bleak House, where the relatively
modern word boredomwas coined, he described chronic boredom
as desolation,amaladyand a monster. Boredom is an un-
pleasant emotion including suboptimal arousal levels and a
thwarted motivation to experience almost anything different or
more arousing than the behaviours and sensations currently
possible (adapted from Mason &Burn, 2011, in press). It arises
when we perceive that there is nothing to door are tired of doing
the same thing(Larson &Richards, 1991), and is accompanied by a
sense of time dragging (Didier-Weil, 1990; Droit-Volet &Meck,
2007; Wahidin, 2006). Fahlman, Mercer-Lynn, Flora, and Eastwood
(2013) suggested boredom includes ve components they labelled
as Disengagement, High Arousal, Low Arousal, Inattention and
Time Perception. Boredom differs from other related states
including frustration (Mason &Burn, 2011, in press), depression,
stress and apathy (Goldberg, Eastwood, Laguardia, &Danckert,
2011). Inescapable boredom is highly distressing (Martin, Sadlo, &
Stew, 2006), and a major torment for human prisoners (in both
the U.S. and U.K.: Hunt, 2006, pp. 37e61; Wahidin, 2006). Human
boredom can be triggered externally by monotonous, meaningless
situations. This can cause work absenteeism, cognitive impairment,
apathy (Harris, 2000), risk taking, alcoholism (Wegner &Flisher,
2009) and abnormal behaviours (such as head banging or rock-
ing; Mendez &Mirea, 1998). Similarly, boredom proneness exists as
a personality trait, predictive of addiction, aggression, depression,
impulsivity, sensation seeking, dangerous driving and juvenile
delinquency (Dahlen, Martin, Ragan, &Kuhlman, 2005; Harris,
2000; Mercer-Lynn, Flora, Fahlman, &Eastwood, 2013; Newberry
&Duncan, 2001). Toohey (2011, page 1) suggested Predictability,
monotony and connement are all keyto triggering boredom.
Although he was mostly writing about human boredom, these
three factors typify captive life for nonhuman animals, so boredom
could be a prevalent and chronic animal welfare problem (Mason &
Burn, 2011; Wemelsfelder, 2005). Boredom is socially and
*Correspondence: C. C. Burn, The Royal Veterinary College, North Mymms AL9
7TA, U.K.
E-mail address: charlotte.burn@worc.oxon.org.
Contents lists available at ScienceDirect
Animal Behaviour
journal homepage: www.elsevier.com/locate/anbehav
http://dx.doi.org/10.1016/j.anbehav.2017.06.006
0003-3472/©2017 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
Animal Behaviour 130 (2017) 141e151
economically important, and it has been studied in human socio-
logical and psychological elds. However, investigation of its bio-
logical basis is just beginning.
Here I aim to help stimulate biological research into boredom in
wild and captive animals. This paper consists of two main sections.
First, I summarize the still rather scant empirical evidence and,
using Tinbergens (1963) framework, explore theoretical argu-
ments for boredom-like states in animals. Second, to enable iden-
tication of potential behavioural and physiological indicators of
boredom, I characterize boredom in terms of its likely behavioural
and physiological manifestations, suggesting how it might be
measured in future research. I cover the valence (pleasantness) and
arousal (wakefulness) qualities of boredom, using them to predict
many likely indicators of boredom. However, not every indicator
ts the valence-arousal framework so I also include other likely
hallmarks of boredom, such as manifestations of perceived slow
passage of time, abnormal behaviour and sleep disruption. Being
able to scientically study objective indicators of boredom has wide
relevance, enabling use of animal models of human boredom,
research into the ethology and evolution of boredom, and scientic
evaluation of the efcacy of interventions to combat human and
animal boredom.
WHY MIGHT NONHUMAN ANIMALS EXPERIENCE BOREDOM?
A dog left home alone for several hours each day energetically
extracts the foam from a well-chewed corner of the sofa, then
whines, yawns and lies awake awhile before getting up again (Lund
&Jørgensen, 1999); Alex, the African grey parrot, having shown
great prowess in naming colours and quantities of numerous ob-
jects, starts to stare at the ceiling, to offer nonsensical answers to
questions, repeatedly preens himself, and requests to go to his cage
or be given water, food or novel treats (Pepperberg, 2013); a labo-
ratory rat sniffs through the bars of its unenriched cage, digs briey
at the sawdust, sniffs the cage walls and nips at a passing cagemate
(Abou-Ismail, Burman, Nicol, &Mendl, 2010); and a farmed pig
with no substrate to chew sits and stares, then stands inactive
awhile, before suddenly chewing a penmate's tail (Studnitz, Jensen,
&Pedersen, 2007). To the naïve observer, the behaviour of each of
these animals may be reminiscent of that of a bored human. Indeed,
the little evidence to date suggests the homology may go deeper
than mere supercial resemblance.
As with any emotion, boredom is private to the individual
experiencing it. Therefore, we cannot be certain that other in-
dividuals, human or otherwise, experience it exactly as we our-
selves do. The term Boredomhas historically been rather taboo in
serious animal behaviour science, being labelled as anthropo-
morphic, or dismissed as trivial compared with some other welfare
issues (Wemelsfelder, 2005). Moreover, boredom is sometimes
assumed to be unique to humans (e.g. Anderson, 2004). Thus, it has
largely been neglected despite its potential prevalence and malig-
nance. However, there are both empirical and theoretical reasons,
as well as ethical ones, to encourage biological exploration of ani-
mal boredom.
Existing Empirical Studies of Animal Boredom
The few studies explicitly aiming to investigate animal boredom
include observations that propensity for behavioural diversity is
signicantly reduced in pigs, Sus scrofa, kept in impoverished en-
vironments for 5 months compared with pigs that received
manipulable substrate (Wemelsfelder, Hunter, Mendl, &Lawrence,
2000). This is consistent with boredom, but also with other ex-
planations, including apathy, depression or cognitive impairment.
Taking a different approach, monotony causes many species to seek
novelty, even novel stimuli they would normally avoid (reviewed in
Berlyne, 1960; Kirkden, 2000; Mason et al., 2013; Stevenson,1983).
For example, despite normally shunning bright light, rats, Rattus
norvegicus, increasingly pressed levers for ashes of light the longer
they were kept in darkness (in Berlyne, 1960). Similarly, rats given
only their preferred food for 3 days and then offered a choice
selected a nonpreferred food, even one previously associated with
sickness (Galef &Whiskin, 2003). Thus, even initially positive
monotony becomes aversive with time.
More recently, clear hypotheses regarding a key hallmark of
boredom, motivation for general stimulation (Meagher, Campbell,
&Mason, in press; Meagher &Mason, 2012), have been tested in
fur-farmed mink, Mustela vison. Compared with mink in environ-
mentally enriched cages, those in standard cages were signicantly
more likely to approach diverse stimuli, ranging from rewarding
cues to (normally) aversive ones. Standard-housed mink also
consumed more snacks and spent more time lying awake inactive,
as is reported in bored humans (Moynihan et al., 2015). Together,
this prole of behaviours enabled Meagher and Mason (2012) to
differentiate boredom from depression or apathy as explanations
for the awake inactivity so prevalent in standard-housed mink.
Hypothetical Ethological Explanations for Animal Boredom
The above examples all originate from studies of captive ani-
mals, understandably as captive animals are subject to inescapable
monotonous situations more than wild ones are. Yet, as captivity is
a relatively recent challenge in evolutionary terms, one might ask
why the ability to experience boredom would have evolved. As so
few studies have explicitly investigated animal boredom, the hy-
pothetical explanations I offer draw on indirect evidence regarding
human boredom or from indirectly relevant phenomena in
nonhuman animals (e.g. impulsivity, neophilia [attraction to nov-
elty] or sensation seeking). I offer suggestions rather than answers.
With this limitation acknowledged, I briey explore how and why
animals might experience boredom, using Tinbergen's (1963) four
levels of explanation as a framework.
Causation of boredom
Causation refers to the immediate internal and external mech-
anisms that trigger individual behaviour, or in this case a behav-
iourally relevant emotion. Causal explanations comprise myriad
mechanisms, ranging from environmental cues to endocrine,
neurological and other physiological signals. As indicated earlier, a
key external trigger for boredom in captive animals will be barren
environments, which may be spatially and/or temporally monoto-
nous. Boredom thus occurs when both external and internal
stimulation are insufcient to maintain optimal arousal (Berlyne,
1960).
The neural mechanisms producing boredom have seemingly not
been investigated even in humans, but the brain's arousal systems
will be relevant. Arousal is nonunitary, instead being distributed
across several different, interconnected brain structures (Calderon,
Kilinc, Maritan, Banavar, &Pfaff, 2016; Jones, 2003). Within the
brainstem, arousal is supported by six systems: (1) long gluta-
minergic nucleus gigantocellularis neurones in the reticular for-
mation, which receive cortical and multisensory peripheral
stimulation and have both ascending (cortical) and descending
(autonomic, neuroendocrine and motor) projections; (2) cholin-
ergic pontomesencephalic neurones, which facilitate awakening
and REM sleep; (3) the mesolimbic dopamine pathway, which
helps elicit all motivations and reward-directed behaviour; (4) the
adjacent nigrostriatal dopamine system, which increases arousal
and reward-directed behaviour, and is involved in time perception
(Jahanshahi, Jones, Dirnberger, &Frith, 2006; Simen &Matell,
C. C. Burn / Animal Behaviour 130 (2017) 141e151142
2016); (5) the serotonergic raphe nuclei, most active during awake
relaxation; and (6) the noradrenergic locus coeruleus, most active
during stress or panic. Activity in these systems is inuenced by,
and relayed to, the cortex and/or the body via further arousal sys-
tems within midbrain structures including the hypothalamus,
thalamus and basal forebrain (Jones, 2003; Calderon et al., 2016).
Most of these systems are highly conserved among vertebrates,
with similar organization in mammals, birds and reptiles at least
(Calderon et al., 2016). Thus, many vertebrates could have the
neurological apparatus to produce boredom-like states.
Boredom might thus result from discrepancy between the ac-
tivations of different arousal systems. For example, because
boredom often occurs when stimulation is lacking, but when
general motivation for stimulation remains high, arousal systems
reliant on sensory information may be relatively inactive, while the
mesolimbic dopamine pathway may be highly active. Also, the lo-
cus coeruleus shifts from phasic to tonic ring, becoming less
active, as nonhuman primates disengage from a task and start
performing nontask-related behaviours (Aston-Jones &Cohen,
2005), possibly indicating task boredom. The insular cortex, inte-
grating emotional, interoceptive and temporal perceptions, is also
likely to be highly active during boredom (Wittmann &Butler,
2016; Wittmann et al., 2011). That boredom might result from
dissonance between arousal systems is consistent with observa-
tions that both stimulant and depressant drugs can relieve human
boredom (Boys et al., 1999; Howard &Zibert, 1990), perhaps by
resolving the discrepancy between motivation for arousal and low
actual arousal.
Whether these systems are sufcient for animals to show
boredom-like aversion to monotony remains to be discovered.
Indeed, perhaps convergent mechanisms could exist in in-
vertebrates, such as octopuses. Octopuses are highly exploratory,
neophilic, with remarkable cognitive abilities (Hochner, Shomrat, &
Fiorito, 2006; Mather &Anderson, 1999), and the term boredom
has been tentatively used as impetus for providing environmental
enrichment to captive octopuses (Anderson &Wood, 2001; Mather,
2001).
Ontogeny of boredom
Ontogeny refers to changes in behavioural machineryduring
development and maturation (Tinbergen, 1963). At a neurological
level, most animals require species-appropriate stimulation to
develop and maintain behavioural exibility and learning abilities
(e.g. Würbel, 2001). The propensity for boredom could motivate
animals to seek appropriate types and intensities of stimulation to
aid this in an age-appropriate manner. This seems true in humans,
with young children easily bored by adult activities, while
repeating games like peek-a-boo, or moving objects in and out of
containers, many times over (Piaget, 2013); and with teenagers
notoriously susceptible to boredom, shifting attention towards
socially relevant memes, sexual information and self-image
(Danesi, 1994). Similar phenomena may occur in nonhuman ani-
mals also; for example, motivation for different types of play
changes with age in several species (Pellis &Iwaniuk, 2004). Also,
boredom-relevant behaviour including risk taking, psychoactive
drug consumption, novelty seeking, and impulsivity all increase in
adolescent rodents compared with juveniles or adults (Laviola,
Macrı, Morley-Fletcher, &Adriani, 2003; Macrı, Adriani, Chiarotti,
&Laviola, 2002).
Much ontogenetic research explores the relative contribution of
genes versus environment to the development of individual
behavioural phenotypes. In humans, boredom proneness is prob-
ably highly heritable, because twin studies reveal high heritability
in gambling (Winters &Rich, 1998) and drunk driving (Anum,
Silberg, &Retchin, 2014). The eld of animal personality
(behavioural syndromes) might be ripe to explore boredom
proneness, discovering whether similar correlations between
boredom proneness and other traits exist in animals as in humans
(Dahlen et al., 2005; Harris, 2000), and the extent of genetic versus
environmental contributions. For example, boldness and proactive
coping styles in animals are associated with neophilia (Carere,
Caramaschi, &Fawcett, 2010), impulsivity and aggressiveness (e.g.
Coppens, de Boer, &Koolhaas, 2010), so bolder or more proactive
animals might also show other correlates of boredom proneness,
e.g. sensation seeking and overestimation of waiting times. Also,
humans with ADHD are highly boredom prone (e.g. Kass, Wallace,
&Vodanovich, 2003), so animal models of putative ADHD should
also show this proneness.
Adaptive value of boredom
Boredom appears to have entirely negative corollaries when
prolonged and inescapable, but to have adaptive value, it must have
positive evolutionary tness effects when it can be acted upon.
Boredom might provide the motivation to stay within optimal
levels of arousal for learning or maximal task performance. The
YerkeseDodson law predicts a U-shaped relationship between
arousal and performance, which is often corroborated (e.g.
Anderson, 1994), but see Wu et al. (2010) for example. Boredom can
arise when tasks are too easy or too difcult, especially if learning is
not achieved (e.g. Acee et al., 2010), so it encourages switching
attention to more rewarding activities. Boredom might also spark
creativity and innovation in animals, as in humans (Mann &
Cadman, 2014). Indeed, captivity can seemingly stimulate innova-
tive behaviours unknown in the wild, such as tool use in otherwise
nontool-using species ranging from elephants to rooks (Haslam,
2013; Tebbich, Seed, Emery, &Clayton, 2007), which could be a
creative response to the monotony of captivity. It remains to be
discovered whether indicators of boredom precede innovation in
real time, and whether signs of boredom proneness are more (or
less) common in more innovative individuals or species. More
innovative species are signicantly more neophilic (Reader, 2003),
so they may show more boredom indicators when faced with
monotony.
Boredom could also prompt exploration and niche diversica-
tion within lifetimes, promoting learning and preventing animals
from becoming behaviourally inexible in the face of likely envi-
ronmental changes. For example, boredom could help motivate
some adolescent animals to leave their natal homes and seek new
territory, stimulate omnivores to sample new foods even when
familiar food is plentiful, or drive innovative species to experiment
and play with new materials when their more immediate needs are
fullled (Held &
Spinka, 2011). In each case, risk comes with new
behaviour, but so does opportunity. In the eld, it could be useful
for conservationists and behavioural ecologists to know whether
indicators of boredom in wild animals can predict the onsetof risky
behaviour.
The negative tness consequences of animals being unable to
escape monotony, or to exercise, explore and/or learn, would usu-
ally be difcult to ascertain in wild animals, because they are rarely
constrained. However, we know from captive animals lacking
sensory or cognitive stimulation to an extreme that neural path-
ways can fail to develop, and those already present can weaken; the
brains of animals in barren environments even become physically
smaller (e.g. Würbel, 2001). This manifests as an increasingly
inexible and limited behavioural repertoire, such as the highly
perseverative stereotypical behaviour seen in animals kept in
barren conditions (Mason &Rushen, 2006). This is unlikely to reach
such a pathological degree in the wild, so we would not expect
natural selection to have prevented extreme synaptic die-off from
happening, but even mild behavioural inexibility could be
C. C. Burn / Animal Behaviour 130 (2017) 141e151 143
detrimental to tness in some wild animals, especially in highly
variable niches.
It is worth noting that boredom may primarily be problematic
for relatively normal captive animals: those still capable of exible,
responsive behaviour. This is because, if understimulation is severe
and prolonged enough to cause central nervous system damage,
boredom may advance into apathy or brain damage, as can happen
in human prisoners (Shalev, 2008, pp. 9e23). Boredom may grad-
ually become irrelevant to apathetic or depressed animals which no
longer seek, or respond normally to, stimulation (Meagher &
Mason, 2012).
Phylogeny of boredom
Phylogenetic explanations apply at the species level, including
how characteristics differ across diverse species. Boredom is most
likely in generalist species, given the proposed adaptive and
developmental value of boredom as a motivator to explore and
learn. Discovering whether this is true will require systematically
comparing the frequency of boredom indicators across a range of
species, using appropriate phylogenetic analysis to control for
species relatedness. This is yet to be done, but generalist traits do
correlate positively with boredom-relevant traits including
neophilia and innovation at the species level (reviewed in Reader,
2003). Further suggestive evidence comes from captivity, where it
seems to be particularly neophilic, generalist species (Kirkden,
2000; Mason et al., 2013; Stevenson, 1983) that proactively seek,
even aversive, stimulation in barren environments.
From an evolutionary psychology perspective, exploration of
which species respond to monotony with boredom-like behaviour
could help answer fundamental questions such as which brain
structures facilitate boredom?(Calderon et al., 2016), are more
intelligentspecies more prone to boredom?(Mason et al., 2013),
and which species are most at risk from the monotony common in
captivity?(Mason et al., 2013).
HOW TO MEASURE ANIMAL BOREDOM
There will not be single unambiguous indicators of boredom, as
with other emotional states, but instead several indicators must be
used together to form a prole consistent with boredom (Mason &
Mendl, 1993). The indicators chosen for any one study will depend
on the species, the relevant timescale (some indicators best reveal
welfare over months, others over seconds), ethical considerations
(e.g. invasiveness) and feasibility (e.g. environmental, time and
nancial constraints).
Increasingly in animal studies (Mendl, Burman, &Paul, 2010),
emotions are classied according to a dimensional model, each
usually described in terms of valence and arousal (Russell, 1978,
1980). Classic examples of emotions that map onto these di-
mensions include fear having high arousal and negative valence, or
relaxation having low arousal and positive valence (Russell, 1978,
1980). The valenceearousal model oversimplies true emotional
complexity, but it aids animal research because the valence and
arousal signicance of much behaviour and physiology is well un-
derstood, enabling predictions about how to measure certain
emotions using objective indicators of both valence and arousal
(Mendl et al., 2010). I use this as a starting point for identifying
potential indicators of animal boredom. However, there are other
important qualities of human boredom that do not t the model, so
I also include some of these (altered time perception, disrupted
sleep and abnormal behaviour). First, I outline theoretical reasons
for suggesting certain indicators, and then offer practical examples.
Theoretical Considerations
Valence and arousal qualities of boredom
There is little dispute that boredom is negatively valenced (e.g.
Eastwood, Frischen, Fenske, &Smilek, 2012; Martin et al., 2006), so
that will not be discussed further, except to highlight that it pre-
dicts animals will attempt to avoid or mitigate boredom-inducing
situations. However, whether arousal during boredom is high or
low has been debated. Berlyne (1960, page 190) argued that
boredom comprises high arousal, stating that sensory depri-
vation becomes aversive when internal factors cause a rise in
arousal and the lack of stimulation renders the cortex incapable of
keeping arousal within bounds. To illustrate, Berlyne (1960, page
189) pointed out that Lying motionless in a quiet dark room is
extremely trying when one is healthy and has had enough sleep.
In contrast, questionnaire respondents usually classify boredom as
comprising relatively low arousal (Burn, 2011; Russell, 1980).
Thus, boredom is paradoxically characterized both by high and
by low arousal (Fahlman et al., 2013), and perhaps this is not sur-
prising now that the multifactorial nature of arousal in the brain
has been revealed (Jones, 2003). As boredom occurs when arousal
inputs are low, but arousal motivation is high, the behavioural and
physiological outputs will reect this conict. This predicts alter-
nation between attempts to raise arousal via motor restlessness or
sensation seeking and low arousal drowsiness, with drowsiness
gradually prevailing if the understimulation continues. As Berlyne
(1960, page 189) said a human being or an animal in the
throes of agonizing boredom shows restlessness, agitation, and
emotional upset [But] lack of stimulation also has a tendency to
put people to sleep. Indeed, it also ts Wemelsfelders (2005, page
85) description of a typical bored animal's behaviour: Over time
the animal appears to become both more lethargic and more irri-
tably reactive; it can never truly relax, and may wander around,
snifng or nibbling different substrates but never staying with any
for long. Note that emotional arousal is not the same as motor
activity (Oxendine, 1970), so even highly active restlessness may
barely raise arousal by other measures.
Boredom must be distinguishable from other aversive states of
suboptimal arousal that may exist (e.g. exhaustion in the face of a
challenge), so one could specify that boredom is caused by
monotony (rather than, say, duration or intensity of energy
expenditure per se). Monotony can be spatial, as in barren envi-
ronments, or temporal, as in repetitive tasks. Boredom appears
unique among negative emotions in being caused by monotony,
which is useful because monotony can be experimentally manip-
ulated enabling comparisons to be made between, for example
barren versus enriched environments, or repetitive versus varied
tasks. In captivity, monotony is generally synonymous with
understimulation, and attempts to relieve it often rely on envi-
ronmental enrichment, so comparing barren with enriched con-
ditions is likely to be a useful experimental paradigm. However,
boredom can also be induced under highly stimulating situations if
that stimulation is perceived as irrelevant and predictable. This
cause of boredom is described by factory workers and school
children (Anderson, 2004), and might be relevant to working ani-
mals performing repetitive tasks. For example, Alex, the African
Grey parrot, was reportedly most likely to baulk at tasks in the
boredmanner described above when tasks were repetitive or
simpler than preceding tasks, or when rewards lacked novelty
(Pepperberg, 2013). Either way, captive animals are often rendered
passive recipients of stimulation, rather than having choice and
control over their experiences and behavioural options
(Wemelsfelder, 2005).
Anal note on this is that some apparent monotony is relevant
and meaningful for animals (e.g. bamboo browsing in the giant
C. C. Burn / Animal Behaviour 130 (2017) 141e151144
panda, Ailuropoda melanoleuca), or can be relaxing (e.g. repetitive
gardening tasks for humans: Pitt, 2014). Individuals in such situa-
tions would not show signs of boredom; they would approach the
situations, rather than avoid them, and would not seek out alter-
native sources of stimulation.
Altered time perception, sleep disruption and abnormal behaviour
Some important qualities of boredom do not t into the valen-
ceearousal model. A key example is altered time perception, which
has a complex relationship with both valence and arousal:
perceived duration appears to lengthen during periods both of
extreme eventfulness and of extreme uneventfulness, and usually,
but not always, with negative valence (Droit-Volet &Meck, 2007;
Flaherty, 1991). The notion that time dragsduring boredom is
pervasive across human cultures (Didier-Weil, 1990; Droit-Volet &
Meck, 20 07; Flaherty, 1991; Wahidin, 2006), and is a key quality of
boredom (Fahlman et al., 2013). Slow perceived time passage has
been demonstrated in experimental manipulations in humans both
in boredom as an acute state (e.g. Hawkins &Tedford,1976) and as a
personality trait (Danckert &Allman, 2005). The relationship even
works in reverse, so humans perceive the same experience as more
boring if a manipulated clock indicates that it lasted longer than it
really did (Sackett, Meyvis, Nelson, Converse, &Sackett, 2010).
Another mistcharacteristic might include disrupted sleep, as
a consequence of boredom that persists across a sleepewake cycle.
The associated suboptimal arousal may cause animals to sleep
earlier than they would otherwise do, but not being tired, the an-
imals' sleep may be relatively brief and/or supercial. Bored ani-
mals may rest more, but sleep less, because their environment is
insufciently stimulating to keep them awake or properly tire them
out.
Finally, abnormal behaviour, especially stereotypic behaviour,
most frequently occurs in negatively valenced situations, but has a
complex relationship with arousal (Mason &Rushen, 2006). People
often intuitively attribute abnormal behaviour to boredom (e.g.
Blackshaw, 1988; Litva, Robinson, &Archer, 2010). However, more
highly stereotypic mink initially showed fewer boredom indicators
than nonstereotypers in barren environments (Meagher &Mason,
2012), and when the work was replicated, no relationship was
found (Meagher, Campbell, &Mason, In Press). Different abnormal
behaviours, despite sharing many behavioural and neurological
features, can have diverse causative factors (Mason, 1991; Mason &
Rushen, 2006). Some might well be caused by boredom, but others
are caused by more specic frustrations, such as inadequate diets or
lack of appropriate nests (Mason &Burn, in press). Such specic
causes may need ruling out before boredom can be concluded as
the cause, limiting the use of abnormal behaviour as an indicator of
boredom. However, if a study seeks to explore whether abnormal
behaviour results from boredom, this could be tested by observing
whether the behaviour is predicted by other indicators of boredom
and is reduced by diverse arousing stimuli (Mason &Burn, in press).
It is worth clarifying that only abnormal or stereotypic behav-
iours that are responsive to external stimuli are likely to be useful in
boredom research, because if they become habitual or reect brain
dysfunction, they no longer differ between situations (Mason &
Rushen, 2006).
Practical Examples of Boredom Indicators
All the above makes it possible to scientically identify animal
boredom, so I provide examples of promising indicators in
Tables 1e3. I attempt to briey summarize evidence for each in-
dicator in the tables but, as explained above, direct evidence of link s
with animal boredom is lacking for most indicators because
research into the subject is only just beginning. Where direct evi-
dence appears absent, I illustrate the potential relevance of the
indicator by using indirect evidence from animals or humans.
Specically, evidence comes from (1) comparisons of animals in
more versus less monotonous environments, and (2) human
research on waiting experiences, sensory deprivation, sensation
seeking and task-related boredom. Where effects of environmental
enrichment on animals is cited, I have excluded research that only
tested social housing or comfortenrichment, because these would
be expected primarily to relieve welfare issues other than boredom
(e.g. provision of shelters or nesting material could relieve specic
frustrations or stress); instead I include studies testing diverse
stimulating enrichments, such as toys, novel objects, puzzle feeders
and exercise apparatus, more likely to relieve boredom. In many
cases, evidence is compatible with boredom but other explanations
cannot be dismissed without further research. However, its inclu-
sion demonstrates feasibility and offers useful empirical observa-
tions upon which to build further research. None of the indicators
uniquely identify boredom; those in Table 1 can indicate certain
other aversions or frustrations, while those in Table 2 can indicate
nonboredom-related fatigue or relaxation. It is the combined
presence of several indicators in monotonous situations that would
indicate boredom.
Aversion to monotony
Potential indications that animals perceive monotonous situa-
tions as aversive are shown in Table 1. These generally fall into two
categories: (1) indicators of aversion to the monotonous situation
per se, such as preference tests and cognitive bias tests; and (2)
indicators that the animal is proactively attempting to create
stimulation, such as via sensation seeking, restlessness and psy-
choactive drug consumption. Escape behaviour is intermediate
between these two types of indicators; indeed, escape is a unifying
theme as the animal attempts to avoid low arousal either by
seeking external stimulation, or by proactively attempting to in-
crease arousal levels internally, for example via restlessness.
Suboptimal arousal
Indicators of the drowsiness, rather than the aversion, aspect of
suboptimal arousal are covered in Table 2. These indicators will
periodically be disrupted by the bouts of restlessness, escape at-
tempts or sensation seeking described above. These activity bouts
might resemble an extinction curve, with intense initial activity,
followed by waning as the animal nds they are ineffective in
raising arousal. Nevertheless, over a prolonged period (several
hours, depending on the species and situation) the overall arousal
of a bored animal will decline. The animal will show increasing
awake inactivity, and will ultimately fall asleep earlier than in more
engaging conditions (Mavjee &Horne, 1994).
The predictions for decreased hypothalamic-pituitary-adrenal
(HPA) and sympathetic-adrenomedullary (SAM) activity are
notable, because lower activity is commonly interpreted as indi-
cating reduced stress and better welfare. For example, glucocorti-
coids are often referred to as stress hormones, and situations that
reduce their chronically elevated concentrations are commonly
perceived as beneting animals (M
ostl &Palme, 2002). Boredom
may be an exception to this general rule, because glucocorticoids
are catabolic, usually associated with raised arousal, so they might
decline in monotonous situations; here higher, rather than lower,
concentrations might indicate better welfare (see Table 2 for
examples). Ultimately, whether this prediction is true depends on
which brain arousal systems are active versus inactive during
boredom (Jones, 2003). Indeed, some repetitive tasks increase SAM
activity (Weber, Fussler, O'Hanlon, Gierer, &Grandjean, 1980), so
C. C. Burn / Animal Behaviour 130 (2017) 141e151 145
Table 1
Suggested indicators of negative valence caused by monotony in animals and humans
Indicator or test Predicted effect of a monotonous versus a
more stimulating situation
Examples of evidence from humans Examples of evidence from nonhuman
animals
Preference test, consumer
demand test
Animals should avoid the monotonous
situation
NF Mink living in a consumer demand
apparatus were least motivated to push a
weighted door to access an empty
compartment compared with six other
options; they pushed signicantly heavier
weights to access a compartment
containing novel objects (Mason, Cooper, &
Clarebrough, 2001).
Similarly, mice living for several days in a
consumer demand apparatus consisting of
a standard cage and a cage consisting of a
mixture of comfort and stimulating
enrichment pushed signicantly greater
weight to access the enriched cage,
especially if they had been previously
reared with enrichment (Latham &Mason,
2010)
Conditioned place preference
or Pavlovian conditioning
Animals should avoid places or cues that
they associate with the monotonous
situation
Workers (N¼292) who had higher job
boredom scores (5-point Likert scales on
e.g. how monotonous is your job/how
slowly does your job pass?) showed
signicantly higher absenteeism rates (%
days missed) (Kass, Vodanovich, &
Callender, 2001)
NF
Cognitive bias or Judgement
bias
Animals should show a more negative
(pessimistic) perception towards an
ambiguous stimulus when living in the
monotonous situation
Boredom proneness is associated with
more negative expectations about the
future (e.g. reviewed in Farmer &
Sundberg, 1986)
A pessimistic-like cognitive bias has been
shown in response to an absence of, or
removal of, stimulating environmental
enrichment in starlings (Bateson &
Matheson, 2007), rats (Brydges et al., 2011)
and pigs (Douglas et al., 2012)
Escape behaviour Animals should perform more escape
behaviour in the monotonous situation
In humans, boredom is a reported cause of
work absenteeism, e.g. workers reporting
higher job boredom ratings missed a
greater proportion of working days (Kass
et al., 2001)
NF
Sensation-seeking behaviour
and distractibility
Animals in the monotonous situation
should more readily approach stimuli
regardless of whether they are positive,
neutral or negative, and be more
distractible in general
When left alone to think for 15 min, 67% of
men and 25% of women voluntarily
administered electric shocks to themselves
(Wilson et al., 2014). With regard to
distractibility, humans performing a 3 h
visual attention task increasingly paid
attention to irrelevant distracting stimuli
over time (Boksem et al., 2005).
Mink without stimulating environmental
enrichment approached 10 stimuli,
including air puffs, predator scent and a
candle, more readily than mink with
enrichment (Meagher &Mason, 2012);
Norway rats pressed levers for ashes of
light when kept in darkness (Berlyne,
1960), and chose sickness-inducing food
when on a monotonous diet (Galef &
Whiskin, 2003)
Restlessness Animals should perform more bouts of self-
directed behaviour, stretching, destructive
behaviour and repetitive displacement
activity in the monotonous situation
Humans in emergency waiting rooms
without visual art paced up and down, got
out of their seats, and stretched
signicantly more than those in rooms with
art (Nanda et al., 2012); Humans on a 1 h
monotonous task reported that rhythmic
leg or nger movements helped them cope
with the boredom (Pattyn, Neyt,
Henderickx, &Soetens, 2008)
An orang-utan performed more self-
scratching and destructive behaviour while
waiting for a reward when delays to the
reward presentation were longer (Elder &
Menzel, 2001)
Psychoactive drug
consumption
Animals should consume psychoactive
drugs more in the monotonous situation
Humans self-report boredom as a major
trigger for taking a variety of psychoactive
drugs ranging from relaxants to stimulants
(e.g. Boys et al., 1999; Howard &Zibert,
1990)
Studies often show that rats in socially and
environmentally complex cages consume
less morphine (e.g. Alexander, Coambs, &
Hadaway, 1978), amphetamine (Bardo,
Klebaur, Valone, &Deaton, 2001)or
cocaine (Gipson, Beckmann, El-Maraghi,
Marusich, &Bardo, 2011) than isolated
conspecics (but see the opposite for
ethanol consumption: Rockman, Gibson, &
Benarroch, 1989), but the effects of social
isolation and monotony are yet to be
separated
Polyphagia A possible form of sensation-seeking (or, if
extreme, abnormal behaviour), animals in
the monotonous situation should eat more
frequently, even excessively
Humans in three different conditions
consumed more snacks when they self-
reported increased boredom (Moynihan
et al., 2015)
Mink without environmental enrichment
consumed more food rewards than mink
with environmental enrichment (Meagher
&Mason, 2012)
C. C. Burn / Animal Behaviour 130 (2017) 141e151146
Table 1 (continued )
Indicator or test Predicted effect of a monotonous versus a
more stimulating situation
Examples of evidence from humans Examples of evidence from nonhuman
animals
Polydipsia As with polyphagia, animals in the
monotonous condition should drink and
urinate more frequently, even excessively
NF Three laboratory rabbits drank and
urinated excessively; no health
abnormalities were found, and provision of
toys and manipulanda successfully reduced
the behaviour (Potter &Borkowski, 1998)
Examples of suggestive evidence to date are offered from human and/or animal studies; many of these did not set out to investigate boredom, so the evidence they provide
requires replication. NF: no evidence found to date.
Table 2
Suggested indicators of suboptimal arousal levels in animals and humans
Indicator or test Predicted effect of a monotonous versus
a more stimulating situation
Examples of evidence from humans Examples of evidence from nonhuman
animals
Hypothalamic-pituitary-adrenal
(HPA) activity
Measures of HPA activity, e.g. cortisol or
corticosterone, should decrease over
time in the monotonous situation
In men (women were not tested),
salivary cortisol was signicantly lower
following a boring, excessively easy,
computer game than after an
appropriately challenging or difcult
game (Keller, Bless, Blomann, &
Kleinb
ohl, 2011)
An orang-utan showed reduced salivary
cortisol when delays to a reward were
longer (Elder &Menzel, 2001). Pigs
reared in barren environments had
lower diurnal salivary cortisol
concentrations than those reared in
larger straw-provisioned pens (de Jong
et al., 2000)
Sympathetic-adrenomedullary
(SAM) activity
Measures of SAM activity, e.g. heart
rate, adrenaline or noradrenaline,
should decrease over time in the
monotonous situation
As reviewed in Thackray (1981) most,
but not all, studies of human
performance during sustained
vigilance, sensory deprivation or
repetitive tasks showed that boredom
or monotony were accompanied by
reduced heart rate, blood pressure,
oxygen consumption, urinary
adrenaline and noradrenaline
NF
Awake inactivity Animals should spend a greater
proportion of time inactive but awake
in the monotonous situation; they may
appear drowsy, a slumpedposture,
and have a glazedappearance to their
eyes
People reported more sleepiness and
had slower reaction times when in
more boring situations (Mavjee &
Horne, 1994)
Mink in standard cages spent
signicantly more time lying inactive
with their eyes open than mink in
enriched cages (Meagher &Mason,
2012)
Electroencephalographic
(EEG) activity
Animals should show increasing
synchrony, especially increased
presence of slow alpha and theta waves,
and decreased fast beta, during the
monotonous situation
Humans performing a 3 h visual
attention task reported increasing
fatigue and showed increasing theta and
lower alpha EEG band power (Boksem
et al., 2005); those performing a 2 h
repetitive task showed increased power
and stronger synchronization, although
this was not frequency specic(Lorist
et al., 2009); drowsy periods during a 1 h
monotonous driving simulation were
classied as showing a higher
proportion of alpha than beta activity
(Yeo et al., 2009)
Beta activity increases in cats, dogs and
monkeys during task performance or
reward anticipation; further, the cat
studies showed it to reduce during
habituation to stimuli and preceding
incorrect trials, suggesting inattention
(reviewed in Wr
obel, 2000)
Respiratory patterns Respiratory rate should decrease and
become more variable as animals yawn
and sigh more in the monotonous
situation
Human yawning is believed to indicate
boredom across human cultures
(Toohey, 2011), but empirical evidence
is scarce: humans asked to record their
own yawning rate reported greater
frequencies and durations of yawning
while watching a 30 min monotonous
screen than a 30 min rock video
(Provine &Hamernik, 1986)
Lions and mandrills yawned most when
inactive but awake (Baenninger, 1987),
and yawning rate correlated positively
with stereotypic performance in horses
(Fureix, Gorecka-Bruzda, Gautier, &
Hausberger, 2011), both of which are
consistent with boredom, but other
explanations cannot be ruled out
Eye blink rate Blink rate should increase in the
monotonous situation
In humans, blink rate increased during a
situation mimicking slowed passage of
time during a repetitive task (Steele
et al., 2004); drowsy periods during a 1 h
monotonous driving simulation were
classied as showing blink durations
longer than 0.5 s (Yeo et al., 2009)
NF
Examples of suggestive evidence to date are offered from human and/or animal studies emany of these did not set out to investigate boredom, so the evidence they provide
requires replication. NF eNo evidence found to date.
C. C. Burn / Animal Behaviour 130 (2017) 141e151 147
either they did not cause boredom, or there could be different types
of boredom reecting the precise discrepancy between arousal
systems.
Brain imaging may be another revealing avenue for future
research. Until recently it has been invasive for animals, but now
positive reinforcement training allows noninvasive electroen-
cephalography (EEG; T
ornqvist et al., 2013) and functional mag-
netic resonance imaging (Berns, Brooks, &Spivak, 2012)in
nonsedated, behaviourally normal dogs. The covert processing that
such techniques can reveal may help separate measures of mental
arousal versus physical activity. For example, human EEGs have
long revealed that active concentration is predominantly associated
with fast beta waves (16e35 Hz), while resting states progress
through slower alpha (8e13 Hz; awake resting), then theta
(4e7 Hz; drowsiness) and nally delta waves (1e4 Hz; sleep), with
increasing synchrony across brain activity (e.g. Boksem, Meijman, &
Lorist, 2005; Lorist et al., 2009; Yeo, Li, Shen, &Wilder-Smith,
2009). Eye blink rate, which increases with drowsiness, can
sometimes be counted visually or it, together with blink duration,
can be quantied via EEG (Steele, Cutmore, James, &Rakotonirainy,
2004; Yeo et al., 2009).
Lastly, regarding indicators of suboptimal arousal, yawning is a
classic behavioural hallmark of boredom in humans across cultures
(Toohey, 2011), and it appears to occur in many vertebrates
including mammals, birds, reptiles and possibly even sh
(Baenninger, 1997). Yawning and sighing might be expected to
occur with generally slowed respiration during boredom. It has
rarely been used in scientic studies of boredom, despite its likely
relevance and the fact that it will normally be easily quantiable, so
it could play a useful role in future research. Yawning also increases
with fatigue (Guggisberg, Mathis, Herrmann, &Hess, 2007; but see
Baenninger,1997) and even ambient temperature (Gallup, Miller, &
Clark, 2009), so experimental designs will need to rule out con-
icting explanations.
Measuring altered time perception, sleep disturbance and abnormal
behaviour
Evidence for the nonvalence-arousal indicators of boredom is
summarized in Table 3. Investigating how monotony affects ani-
mals' time perception is an exciting new avenue for research, but
it rst requires validation using human verbal report as gold
standard, to help rene paradigms for use in animals. This is
because even human investigations have rarely tested effects of
boredom on timing, and usually test timescales too short to be
relevant (e.g. seconds; Wittmann et al., 2011). Also, they have
sometimes yielded surprising results. For example, subjective
estimation of durations is greatly affected by whether humans
know in advance that they must estimate the duration (so they
consciously attend to the time passage, perhaps like a trained
animal would) versus whether they are only asked to estimate it
in retrospect (Block, Hancock, &Zakay, 2000). Humans report
time to drag (they underproduce durations [e.g. stopping at 8 s
when asked to produce a 10 s interval] and overestimate them
[e.g. estimating the 10 s interval lasted 12 s]) within a monoto-
nous experience; however, if asked retrospectively how long the
monotony lasted, they sometimes underestimate duration
compared with more complex experiences (Block, 1978). Time
drags during monotony, but there is little to remember after-
wards. Further analysis of this is outside the scope of this paper,
but there are well-developed models of temporal encoding within
the brain (e.g. Buhusi &Meck, 2005; Droit-Volet &Meck, 2007;
Simen &Matell, 2016), which will help rene predictions and
paradigms.
This said, time perception can already be objectively measured
in animals. Fixed intervalor peak proceduremethods assess
perception of concurrent (rather than remembered) time, and
involve training animals to expect a certain event after a predict-
able period. Suitable events must elicit distinctive responses in the
animal, for example clear anticipatory behaviour, such as pecking a
Table 3
Suggested indicators of other key characteristics of boredom in animals and humans
Indicator or test Predicted effect of a monotonous versus
a more stimulating situation
Examples of evidence from humans Examples of evidence from nonhuman
animals
Time perception Time should be perceived as passing
more slowly in the monotonous
situation, indicated using e.g. interval
timing paradigms, duration
reproduction paradigms, clock-
watching behaviourand/or onset of
anticipatory behaviour
Humans listening to boringstories
reported them as being relatively
longer than interestingstories
(Hawkins &Tedford, 1976); People
with ADHD, who are often also highly
boredom prone, show signs of time
dragging, such as shorter duration
reproductions, e.g. indicating that they
perceive 10 s to have passed after only
8 s (reviewed in Noreika, Falter, &
Rubia, 2013)
Rats in peak interval (Paule et al., 1999)
or temporal bisection (Meck, 1983)
tasks showed behaviour consistent
with time dragging (faster internal
clock speed) when given
metamphetamine, which increases
dopamine release; this is consistent
with the proposed increase in midbrain
dopaminergic activity, with its
corresponding motivation for increased
stimulation, during boredom (although
metamphetamine itself does not cause
boredom)
Disrupted sleep Across sleepewake cycles, animals
should sleep less (despite being awake
inactive more) in the monotonous
situation
Boredom was a cause of disturbed sleep
cited both by patients and nurses in a
hospital (Lei et al., 2009)
Rats in standard cages had fewer
apparent sleeping bouts and shorter
total durations of sleep than those in
cages with a mixture of comfort
enrichment and novel, stimulating
enrichment (Abou-Ismail et al., 2010)
Abnormal and repetitive
behaviour
Animals should increase performance
of diverse abnormal or repetitive
behaviours in the monotonous situation
(unless the behaviour has become
highly perseverative)
Boredom or understimulation is
reported as causing many abnormal or
repetitive behaviours in humans (e.g.
Fazzi et al., 1999; Mendez &Mirea,
1998; Newberry &Duncan, 2001)
A meta-analysis of 54 published studies
found that 90% of stereotypic behaviour
measurements in zoo mammals were
reduced by stimulating environmental
enrichment provision (Shyne, 2006).
Barren environments cause abnormal
repetitive behaviour in diverse species
(e.g. Mason &Rushen, 2006)
Examples of suggestive evidence to date are offered from human and/or animal studies; many of these did not set out to investigate boredom, so the evidence they provide
requires replication.
C. C. Burn / Animal Behaviour 130 (2017) 141e151148
key in starlings, Sturnus vulgaris, trained to expect a reward
(Bateson &Kacelnik, 1995). Once training is complete, the onset of
the anticipatory behaviour can be compared between conditions
that should or should not promote boredom; animals should start
to perform the anticipatory behaviour earlier under monotonous
conditions.
Alternative paradigms include time discriminationor tempo-
ral bisectiontasks (e.g. Meck, 1996). Here, animals learn that if a
stimulus lasted a short time, they must perform a behaviour (A)
for a reward, and if it lasted a long time, they must perform
behaviour Binstead. They could then be exposed to intermediate
stimulus durations under monotonous versus stimulating condi-
tions, with the prediction that they will more frequently perform
behaviour A under the monotonous condition (Block et al., 2000).
A third insight into an animal's perception of time passage could
be to simulate clock-watchingbehaviour. Humans become more
conscious of time passage when bored, more frequently seeking
feedback on it by, for example, looking at clocks (Eastwood et al.,
2012; Pulce, 2005). Animals would need to learn that a simple
salient clock, like a sand-timer or a slider, predicts time until an
awaited event, and the experimental paradigm would need the
animal to behave distinctively when checking the clock, for
example peering around a barrier at it. They should perform this
behaviour more frequently in monotonous situations, and the fre-
quency should increase with absolute duration.
Regarding measurement of sleep, this is usually done by
recording when animals have adopted a sleep posture with their
eyes closed for a dened minimum amount of time (Abou-Ismail
et al., 2010); sleep itself is a subjective state, so animals some-
times appear asleep when still aware of their surroundings. Sleep
postures are thus a proxy for actual sleep, but use of noninvasive
brain imaging also opens new possibilities for objectively dis-
tinguishing between different sleep phases and sleep quality
(H
anninen, M
akel
a, Rushen, de Passill
e, &Saloniemi, 2008).
Boredom can lead to disrupted sleep in humans (Lei et al., 2009)
and possibly in rats (Abou-Ismail et al., 2010;Table 3).
Finally, bearing in mind the caveats about using abnormal or
repetitive behaviour to indicate boredom, some predictions can
be made. When such behaviour indicates boredom, rather than
specic frustration, individual animals may perform more than
one type of abnormal behaviour in their attempts to generate
some, any, stimulation. This seems true in humans, where bored
individuals may exhibit any or all of leg joggling, drumming n-
gers, pacing, hair twirling, rocking or even their own idiosyncratic
behaviour (e.g. Fazzi et al., 1999; Mendez &Mirea, 1998;
Newberry &Duncan, 2001). Similarly, because boredom in-
cludes motivation to experience something, anything, else
(Mason &Burn, in press), boredom-induced abnormal behaviour
should decrease in response to diverse stimulating interventions,
including novel objects, sensory experiences, exercise apparatus
and more, whether positive or negative (Berlyne, 1960; Meagher
&Mason, 2012).
CONCLUSIONS
Boredom is not the trivial annoyance it is sometimes dismissed
as. Animal boredom is biologically plausible: animals avoid
monotony and seek stimulation, and there is gathering evidence for
its mechanism in vertebrates, its role in ontogeny, and its adaptive
value in maintaining behavioural exibility, especially in generalist
species. Behavioural and physiological indicators will signify aver-
sion to monotony and suboptimal arousal, as well as perceived
slowing of time. Biological study of boredom is so scarce that some
research will rst need validation in humans, using self-reported
boredom as a gold standard (Burn, 2011), before extrapolating to
animals.
Too often animal boredom has been dismissed as an anthro-
pomorphic concept, or as a luxury compared with other more
widely accepted welfare issues such as pain or stress
(Wemelsfelder, 2005). However, given the intense distress that
prolonged boredom can cause in humans, and the cognitive dam-
age to which understimulation can ultimately lead, it is potentially
a severe and highly prevalent animal welfare issue neglected too
long. The time is ripe to embrace animal boredom as a topic of
genuine scientic and moral interest, allowing us to explore the
biological basis of boredom in animal models, and to evaluate in-
terventions to combat boredom and its associated problems in
humans and animals alike.
Acknowledgments
Many thanks to Alex Weir, Georgia Mason, Becky Meagher, Mike
Mendl, Elizabeth Paul, Andrea Polanco and the anonymous referees
for their inspiration and/or valuable comments. Thanks also to the
27 volunteers from the Royal Veterinary College who took the time
to complete a questionnaire and pilot study on boredom (Burn,
2011; Ethics approval number: URN 2010 1036), assisted by
Emma Davey and Matthew Parker, which helped rene my ideas.
Much of the work underpinning this essay was conducted while I
was supported by a Wellcome Trust Value in People Fellowship
(AXAK97 (1429)), and the questionnaire and pilot study were
supported by the Royal Veterinary College Internal Grant Scheme
(VPR.BURC 1113). The submitted manuscript (PPH_01074) was
approved according to The Royal Veterinary College's internal
process.
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... The Boredom Choice Task. In order to study boredom in the context of a defined task that both induces boredom to a controllable degree and at the same time provides a behavioral readout, we focused on a consensus definition of a well operationalizable key feature of boredom, namely negative affect 1,[33][34][35] . We measured the participants' degree of avoidance of different sources of sensory stimulation that varied in their level of monotony 1,34 . ...
... In order to study boredom in the context of a defined task that both induces boredom to a controllable degree and at the same time provides a behavioral readout, we focused on a consensus definition of a well operationalizable key feature of boredom, namely negative affect 1,[33][34][35] . We measured the participants' degree of avoidance of different sources of sensory stimulation that varied in their level of monotony 1,34 . Participants were instructed to perform a repeated two-alternative forced choice task, in which each alternative was coupled with the presentation of different sensory stimuli (Fig. 1A). ...
... Nevertheless, future studies could use the Boredom Choice Task to study the interaction between boredom, deficient coping strategies with boredom and mental disorders such as ADHD and depression, that have well-established links to boredom [7][8][9][10][11] . In conclusion, the simplicity and nonverbal nature of the Boredom Choice Task represents a standardized framework for the study of boredom that can be used in healthy and clinical populations and, uniquely, in non-human species 34,49 . Compared to studies in humans, the translation to model organisms could enable investigations of the neural basis of boredom-related behavior, offering a wider spectrum of neural manipulations and measurements of brain activity. ...
Article
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Boredom has been defined as an aversive mental state that is induced by the disability to engage in satisfying activity, most often experienced in monotonous environments. However, current understanding of the situational factors inducing boredom and driving subsequent behavior remains incomplete. Here, we introduce a two-alternative forced-choice task coupled with sensory stimulation of different degrees of monotony. We find that human subjects develop a bias in decision-making, avoiding the more monotonous alternative that is correlated with self-reported state boredom. This finding was replicated in independent laboratory and online experiments and proved to be specific for the induction of boredom rather than curiosity. Furthermore, using theoretical modeling we show that the entropy in the sequence of individually experienced stimuli, a measure of information gain, serves as a major determinant to predict choice behavior in the task. With this, we underline the relevance of boredom for driving behavioral responses that ensure a lasting stream of information to the brain.
... Few studies have directly addressed the issue of animal boredom so far. However, based on the ndings from human studies 21,22 , some behavioral abnormalities observed in captive animals can be readily linked to boredom 23 . ...
... Another symptom of human boredom is an altered perception of time, in which time does not seem to pass in monotonous situations 26 . In animals, this phenomenon can be measured objectively by training them to expect a speci c event or reward after a predictable period and measuring their anticipatory behavior after being exposed to monotonous tasks or environments 23 . This method was successfully trained in starlings using pecking a key as an anticipatory behavior 27 . ...
... Since a su cient form of stimulation is lacking in boring situations, sensation-seeking or stimulusseeking behavior also occurs in animals 23 . This is seen as a form of escape from the unpleasant, boring situation. ...
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Boredom is an emotional state that occurs when an individual has nothing to do, is not interested in the surrounding, and feels dreary and in a monotony. While this condition is usually defined for humans, it may very well describe the lives of many laboratory animals housed in small, barren cages. To make the cages less monotonous, environmental enrichment is often proposed. Although housing in a stimulating environment is still used predominantly as a luxury good and for treatment in preclinical research, enrichment is increasingly recognized as a way to improve animal welfare. To gain insight into how stimulating environment influences the welfare of laboratory rodents, we conducted a systematic review of studies that analyzed the effect of enriched environment on behavioral parameters of animal wellbeing. Remarkably, a considerable number of these parameters can be associated with symptoms of boredom. Our findings show that a stimulating living environment is essential for the development of natural behavior and animal welfare of laboratory rats and mice alike, regardless of age and sex. Conversely, confinement and under-stimulation in conventional housing systems has potentially detrimental effects on the mental and physical health of laboratory rodents. We show that boredom in experimental animals is measurable and does not have to be accepted as inevitable.
... Conversely, hypo or low levels of stimulation can also have a dramatic impact on sleep. Low levels of stimulation (often connotated with boredom) (189) leads to lethargy and mental fatigue that may result in the animal sleeping earlier than usual or resting more, as the environment offers no opportunities to keep them awake or tire them out (189,190). In this sense, increased TST is not always an indicator of positive welfare. Several studies (50,151,191) have shown that sleep quality is related to daily activity level, such that poor sleep quality arises from inactivity or proneness toward sedentary lifestyles. ...
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Sleep is a significant biological requirement for all living mammals due to its restorative properties and its cognitive role in memory consolidation. Sleep is ubiquitous amongst all mammals but sleep profiles differ between species dependent upon a range of biological and environmental factors. Given the functional importance of sleep, it is important to understand these differences in order to ensure good physical and psychological wellbeing for domesticated animals. This review focuses specifically on the domestic horse and aims to consolidate current information on equine sleep, in relation to other species, in order to (a) identify both quantitatively and qualitatively what constitutes normal sleep in the horse, (b) identify optimal methods to measure equine sleep (logistically and in terms of accuracy), (c) determine whether changes in equine sleep quantity and quality reflect changes in the animal's welfare, and (d) recognize the primary factors that affect the quantity and quality of equine sleep. The review then discusses gaps in current knowledge and uses this information to identify and set the direction of future equine sleep research with the ultimate aim of improving equine performance and welfare. The conclusions from this review are also contextualized within the current discussions around the “social license” of horse use from a welfare perspective.
... The authors suggested rotating a large number of different items in an unpredictable order to minimise habituation to EE. Consequently, respondents who reported changing EE with only a monthly frequency are potentially reducing the effectiveness of their EE and creating a monotonous and unstimulating environment, risking boredom [11,48]. One caveat is that ferrets may benefit from less regular changing of EE that is intended to promote rest, sleep or refuge, which may provide security in their permanence [49]. ...
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Ferrets (Mustela putorius furo) are kept and used in multiple sectors of society, but little is known about how they are housed and what environmental enrichment (EE) they may benefit from. We aimed to help guide caretakers about what housing and EE can be provided for ferrets. Through an online questionnaire of ferret caretakers, including pet, laboratory, zoological collection, rescue and working animal sectors internationally, we described ferret housing, opportunities for exploration, EE provision and caretaker opinions on ferrets’ preferred EE types, and problematic EE. In total, 754 valid responses from 17 countries were analysed, with most (82.4%) coming from pet owners. Most ferrets were housed socially, with housing varying across sectors from single-level cages to free-range housing in a room or outdoor enclosure; pet owners mostly used multi-level cages. The most commonly reported EE included hammocks, tunnels and tactile interaction with caretakers. Respondents reported that ferrets particularly enjoyed digging substrates, tunnels, human interaction and exploration. The most frequently reported problems were that ingestion of unsuitable chew toys and rubber items could cause internal blockages, narrow tunnels could trap ferrets, and certain fabrics that could catch claws. This suggests a need for increased awareness of the risks of these EE types and for more commercially available safety-tested ferret EE. Scent trails were relatively rarely provided but were reported to be enjoyed and harmless, so we recommend that these should be provided more commonly. Our results suggest that there is scope to improve ferret housing and EE provision to benefit ferret welfare across all sectors.
... Pigs are reared in barren housing environments in the breeding, weaning and fattening phases. Monotonous environments generate boredom, a negative emotional state [33]. High stocking densities exacerbate the problems of barren environments, resulting in aggression and redirected behaviours performed on conspecifics [34]. ...
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Preventative measures, such as biosecurity and vaccinations, are essential but not sufficient to ensure high standards of health in pig production systems. Restrictive, barren housing and many widely used management practices that cause pain and stress predispose high-performance pigs reared in intensive systems to disease. In this context, antibiotics are used as part of the infrastructure that sustains health and high levels of production in pig farms. Antimicrobial resistance (AMR) is a global emergency affecting human and animal health, and the use of antibiotics (AMU) in intensive livestock farming is considered an important risk factor for the emergence and spread of resistant bacteria from animals to humans. Tackling the issue of AMR demands profound changes in AMU, e.g., reducing their use for prophylaxis and ending it for growth promotion. In support of such recommendations, we revise the link between animal welfare and AMU and argue that it is crucial to sustainably reduce AMU while ensuring that pigs can live happy lives. In support of such recommendations, we aimed to revise the link between animal welfare and AMU in pigs by analysing stress factors related to housing and management and their impact on pig welfare. In particular, we reviewed critical management practices that increase stress and, therefore, pigs’ susceptibility to disease and reduce the quality of life of pigs. We also reviewed some alternatives that can be adopted in pig farms to improve animal welfare and that go beyond the reduction in stress. By minimising environmental and management stressors, pigs can become more immunocompetent and prepared to overcome pathogenic challenges. This outcome can contribute to reducing AMU and the risk of AMR while simultaneously improving the quality of life of pigs and, ultimately, maintaining the pig industry’s social license.
... As Miro's shape and size of the ears are very similar to a rabbit's ears, we referred to the literature on the behaviour of rabbits [47] to specify the angle of ears for each emotion, while we also referred to the literature on mice behaviour, which describes ear rotation in detail [44]. Furthermore, for body movements, along with inspiration from animal behaviour (e.g., being mostly inactive and looking drowsy when animals are bored [48]), we referred to humans (e.g., moving backwards when being afraid) and cartoon characters (e.g., moving the head away when disgusted). Also, the design of the robot's movements of the eye lids were mostly based on humans (e.g., wide eyes for surprise [49]), as we assumed that it could be more intuitively understood by humans. ...
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This article proposes design guidelines for 11 affective expressions for the Miro robot, and evaluates the expressions through an online video study with 116 participants. All expressions were recognized significantly above the chance level. For six of the expressions, the correct response was selected significantly more than the others, while more than one emotion was associated to some other expressions. Design decisions and the robot’s limitations that led to selecting other expressions, along with the correct expression, are discussed. We also investigated how participants’ abilities to recognize human and animal emotions, their tendency to anthropomorphize, and their familiarity with and attitudes towards animals and pets might have influenced the recognition of the robot’s affective expressions. Results show significant impact of human emotion recognition, difficulty in understanding animal emotions, and anthropomorphism tendency on recognition of Robot’s expressions. We did not find such effects regarding familiarity with/attitudes towards animals/pets in terms of how they influenced participants’ recognition of the designed affective expressions. We further studied how the robot is perceived in general and showed that it is mostly perceived to be gender neutral, and, while it is often associated with a dog or a rabbit, it can also be perceived as a variety of other animals.
Article
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Boredom is an emotional state that occurs when an individual has nothing to do, is not interested in the surrounding, and feels dreary and in a monotony. While this condition is usually defined for humans, it may very well describe the lives of many laboratory animals housed in small, barren cages. To make the cages less monotonous, environmental enrichment is often proposed. Although housing in a stimulating environment is still used predominantly as a luxury good and for treatment in preclinical research, enrichment is increasingly recognized to improve animal welfare. To gain insight into how stimulating environments influence the welfare of laboratory rodents, we conducted a systematic review of studies that analyzed the effect of enriched environment on behavioral parameters of animal well–being. Remarkably, a considerable number of these parameters can be associated with symptoms of boredom. Our findings show that a stimulating living environment is essential for the development of natural behavior and animal welfare of laboratory rats and mice alike, regardless of age and sex. Conversely, confinement and under-stimulation has potentially detrimental effects on the mental and physical health of laboratory rodents. We show that boredom in experimental animals is measurable and does not have to be accepted as inevitable.
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In this article, creativity is defined as a semiotic phenomenon, as a process in which the boundaries of habits and norms of social communication are exceeded and by which the challenges offered by the environment are solved. Here it is indicated that there is a direct link between attention and animal creativity and shown that there are at least two possibilities for creativity to work – one that needs attention and one which doesn’t. Animal creativity can work through several different mechanisms, which are here combined into a new model. Adding the Uexküllian concepts of the functional cycle and search tone to the model of creativity makes it possible to describe some additional mechanisms of animal creative behaviours. Additional concepts compared include dual memory systems, the theory of associations, and finally Gregory Bateson’s double description. By considering that approach, it is possible to understand how animals find and adapt new behaviours to their repertoires. Researching the creative behaviours of animals and the spread of innovation between populations is important from a wider perspective to understand how animals can adapt to changing environmental conditions.
Chapter
Providing behavioral care to animals in special circumstances, such as following a natural disaster or after removal from a cruelty or neglect situation, presents a variety of unique challenges. Following disasters, animals are often held in rudimentary field shelters until they are reunited with their owners or considered unclaimed. Cruelty cases involve populations of animals, such as dogs from organized dogfighting operations and animals from hoarding situations, that present with behavioral needs for safe and humane sheltering. Long‐term holds, often due to legal cases, compound shelter stress over time, which can lead to behavioral decline. These special circumstances represent substantial challenges to maintaining animal welfare. Even when faced with less‐than‐ideal conditions and other limitations, best efforts should be made to prevent, mitigate, or eliminate negative welfare and to facilitate psychological well‐being.
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Abnormal behaviour in captive animals is both pervasive and ambiguous. Although individual differences are central to the field of animal welfare, studies on abnormal behaviour predominantly employ quantitative, population-level approaches. For example, whereas previous studies on chimpanzee ( Pan troglodytes ) abnormal behaviour have reported significant variation between groups or individuals in the quantity (eg frequency and duration) of abnormal behaviour, much less is known about qualitative differences. Individual abnormal behavioural repertoires may be highly idiosyncratic, where certain behaviours are over-represented (ie individually specific abnormal behavioural 'signatures'). The present study investigated qualitative individual variation in the abnormal behaviour of chimpanzees (n = 15) housed at Royal Burgers' Zoo in Arnhem, The Netherlands. Substantial variation was found between individuals in the diversity (size and evenness) and overall composition of their abnormal behavioural repertoires. Factors including age, sex, and rank did not significantly account for dissimilarity of individuals' abnormal behavioural repertoires, but kin dyads showed more similar abnormal behaviour than non-kin dyads. Further exploratory analyses examined whether individual variation in one abnormal behaviour (coprophagy) predicted variation in stress-related behaviour (self-scratching). This allowed us to tentatively conclude that there were also individual differences in the link between a given abnormal behaviour and the behavioural expression of stress. Qualitative individual variation in abnormal behaviour provides a novel angle to a literature traditionally focused on quantifying abnormal behaviour at the group- or species-level and may thus represent an important yet previously overlooked source of variation in the extent to which abnormal behaviour reflects the state of individual welfare.
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Animals use the neurotransmitter dopamine to encode the relationship between their responses and reward. Reinforcement learning theory ( 1 ) successfully explains the role of phasic bursts of dopamine in terms of future reward maximization. Yet, dopamine clearly plays other roles in shaping behavior that have no obvious relationship to reinforcement learning, including modulating the rate at which our subjective sense of time grows in real time. On page 1273 of this issue, Soares et al. ( 2 ) closely examine the role of dopamine in mice performing a task in which they keep track of the time between two events and make decisions about this temporal duration. The results suggest the need to reassess the leading theory of dopamine function in timing—the dopamine clock hypothesis ( 3 ). They may also help explain empirical phenomena that challenge the reinforcement learning account of dopamine function.
Chapter
Captivity often restricts animals' abilities to perform natural behaviour and explore novel stimuli. Here, we review how this constraint affects psychological welfare by preventing the meeting of motivations. One means by which this happens is through frustrating specific motivations pertaining to particular behavioural systems. This can occur when constrained behaviours are 'behavioural needs': activities tha